Some experiences on the way to biological single ion experiments

One of the experimental cornerstones on the way to the irradiation of singl e biological cells with single, precisely aimed high energy ions is the rel iable detection of hits. Another one is the necessity to keep the cells wet during irradiation. Therefore, the cells have to be separated from the mic roprobe vacuum by a thin window. This window should be extremely thin to mi nimise scattering. At the same time it should be strong enough to withstand atmospheric pressure and it should be radiation hard. During a previous co nference Cholewa et al. [Nucl, Instr. and Meth. B 130 (1997) 275] proposed to use a thin diamond foil to serve as vacuum window and as part of the hit detection system. Later, Kamiya et al. [Appl. Phys. Lett. 71 (13) (1997) 1 875] tested the hit detection efficiency for alpha-particles using boron-do ped diamond. To confirm these results for heavy ions we have checked the re lative merits of diamond foils compared to those of other materials. In add ition to this we have looked for other sources of problems which might prev ent us from hitting single cells with the desired accuracy of 99.9%. (C) 20 01 Elsevier Science B.V. All rights reserved.